1. Field of the Invention
The systems and methods of this invention relate to direct electrical stimulation of nerves, nerve bundles, nerve tissue, and regions in proximity to nerves of the body to treat a variety of medical conditions. Specifically, the present invention relates to methods and apparatus for applying such stimulation to selected nerves without the use of conventional lead/electrode systems.
2. Description of the Background Art
Electrical stimulation of nerves, nerve roots, and/or other nerve bundles for the purpose of treating patients has been known and actively practiced for several decades. Application of an electrical field between electrodes to stimulate nerve tissues is known to effectively modify signal pathways both with unidirectional and bidirectional stimulation along the nervous system to signal the brain or to signal organs to alleviate symptoms or control function. These applications are currently practiced with, both, externally applied devices and implanted devices. For example, applying specific electrical pulses to nerve tissue or to peripheral nerve fibers that corresponds to regions of the body afflicted with chronic pain can induce paresthesia, or a subjective sensation of numbness or tingling, or can in effect block pain transmission to the brain from the pain-afflicted regions. Many other examples include electrical stimulation of various branches of the vagus nerve bundle for control of heart rate, mediating hypertension, treating congestive heart failure, controlling movement disorders, treating obesity, treating migraine headache, and effecting the urinary, gastrointestinal, and/or other pelvic structure in order to treat urgency frequency, urinary incontinence, and/or fecal incontinence. Still other branches of the vagus nerve have been used to treat neuropsychiatric disorders. Additionally, applications are also known for electrical stimulation of nerves and nerve bundles in many other specific, selected nerve regions: for example, the pudendal or sacral nerves for controlling the lower urinary tract.
Depending on the individual patient, direct nerve stimulation can effectively modify signal pathways along the nerve, to and from the brain, and to and from organs in the body and thus provide relief of symptoms or control of bodily function. Treatment regimens and targeted nerve locations are known in related art through use of current, common stimulation devices and methods. Commonly implanted devices for nerve stimulation are made by such companies as Cyberonics, Medtronic, Advanced Bionics, and others.
The nervous system is a complex anatomical network that is organized to connect the brain to all areas of the body. The brain uses the nervous system to control bodily processes and adjust the body to its environment. The nervous system is conceptualized by two parts; the central nervous system (CNS), and the peripheral nervous system (PNS). The CNS generally consists of the brain and the spinal cord. The PNS consists of a series of nerves and nerve bundles branching out to all organs and tissue areas of the body. The PNS is connected to the CNS and thus together provides the network of control between the brain and all specific bodily functions. As illustrated in FIG. 1, the central nervous system is pervasive throughout the body with individual nerves and nerve bundles reaching to all bodily functions. The PNS consists of the cervical, thoracic, lumbar, and sacral nerve trunks leading away from the spine to all regions of the body. The peripheral nervous system also includes cranial nerves. Sensory and control signals travel between the brain and other regions of the body using this network of nerves that all travel along the spinal cord.
Transcutaneous electrical nerve stimulation (TENS) is a well known medical treatment used primarily for symptomatic relief and management of chronic intractable pain and as an adjunctive treatment in the management of post surgical and post traumatic acute pain. TENS involves the application of electrical pulses to the skin of a patient, which pulses are generally of a low frequency and are intended to affect the nervous system in such a way as to suppress the sensation of pain, in the area that the electrodes are applied. This typically would be indicated for use in acute or chronic injury or otherwise used as a protective mechanism against pain. Typically, two electrodes are secured to the skin at appropriately selected locations. Mild electrical impulses are then passed into the skin through the electrodes to interact with the nerves lying thereunder. As a symptomatic treatment, TENS has proven to effectively reduce both chronic and acute pain of patients.
In the context of this application, Specific Nerve Stimulation (SNS) refers to treatments for a variety of medical conditions that apply electrical stimulation directly to nerves, nerve roots, nerve bundles, tissue or regions in proximity to nerves that are in the PNS. Currently available stimulator systems for SNS are fully implanted electronic devices placed subcutaneously under the skin and connected via insulated metal lead(s) to electrodes which are invasively inserted into, around, or onto a nerve or proximate the nerve. A common implanted SNS system contains a battery to power the system. Some implanted SNS systems use an RF wireless connection instead of a battery to power the implanted device. In these RF systems, a receiver device is implanted subcutaneously and a transmitter is worn on the outside of the body. The antenna are tuned to each other and aligned such that control information and power is transmitted to the receiver and then directs the electrical impulses to the electrodes through the leads. The external transmitter contains batteries to power the transmission. All systems have the capability to externally adjust settings of the implanted system through a programming device.
In SNS and TENS systems, electrical energy is delivered through lead wires to the electrodes. For SNS, implanted electrodes are positioned on, around, or in close proximity of the nerve to be stimulated. SNS uses the implanted electrodes to deliver a variety of stimulation modalities including unidirectional and bidirectional propagation along the nerve with the electric pulse waveform defined by a plurality of variables, including, pulse width, pulse frequency (Hz) or duty cycle, amplitude (V), and waveform shape (e.g., mono-phasic or bi-phasic).
SNS is used for treatment of headache, migraine headache, or facial pain by selection of branches in the peripheral nervous system in the cranium or along the vagus nerve bundle. SNS is used for the treatment of chronic pelvic pain due to such conditions as lumbosacral radiculitis, lumbosacral radiculopathy, lumbosacral plexitis, lumbosacral plexopathy, vulvadynia, coccygodynia, peripheral neuritis, and peripheral neuropathy, by applying stimulation to the peripheral nervous system in the sacrum.
SNS is also applied to branches of the vagus nerve in a wide variety of applications, but not limited to the treatment of heart failure; hypertension; obesity; migraine; neuropsychiatric disorders; urinary, gastrointestinal, and/or other pelvic area structures in order to treat urinary urgency, urinary incontinence, and/or fecal incontinence. SNS is also used for severe chronic pain. Stimulation of specific nerves is known to reduce symptoms and enhance the quality of life in patients with chronic pain.
As described above, TENS and SNS devices are battery-powered electronic devices either used transcutaneously (TENS) or implanted (SNS) and connected via insulated metal lead(s) to electrodes which are either placed on the skin (TENS) over the spine or implanted onto, around, or in close proximity to the nerve or nerve bundle selected for stimulation. The implanted electrodes for SNS are positioned on leads that are placed percutaneously, through needle punctures, or through minimally invasive surgical procedures such as laminectomy, or through direct surgical access to position the electrodes on, around, or in proximity to the targeted nerve. On some leads, between 2 and 16 electrodes are available and are positioned in the region that is targeted for electrical stimulation. The implanted leads are then subcutaneously tunneled to the pulse generator (also referred to as a controller) that is implanted in a subcutaneous pocket. The use of these lead wires is associated with significant problems such as complications due to infection, lead failure, lead migration, and electrode/lead dislodgement. Application of electrodes to the nerves can be difficult because of the need to precisely locate electrodes for effective therapy.
Other prior art has attempted to deal with the complications and limitations imposed by the use of electrical leads. For example, self-contained implantable microstimulators and remotely powered microstimulators have been described; however each approach suffers from some significant limitation. A self-contained microstimulator must incorporate a battery or some other power supply; this imposes constraints on size, device lifetime, available stimulation energy, or all three. Due to high use or high energy requirements of the therapeutic stimulation some SNS devices contain recharageable batteries or are powered remotely with an RF coupling to the controller.
For leadless solutions in other similar stimulation applications, remotely powered devices have previously utilized either radiofrequency (RF) or electromagnetic transformer power transmission. RF energy transmission, unless the transmitting and receiving antennae are placed in close proximity, suffers from inefficiency and limited safe power transfer capabilities, limiting its usefulness in applications where recharging or stimulation must be accomplished at any significant depth (>1-2 cm) within the body, in particular where it is desired to permanently implant both the transmitter and receiver-stimulator. Electromagnetic coupling can more efficiently transfer electrical power, and can safely transfer higher levels of power (devices with capacity in excess of 20 Watts have been produced), but again relies on close proximity between transmitting and receiving coils, or the utilization of relatively large devices for deeper (5-8 cm maximum) implantation.
The methods and apparatus of the current invention utilize vibrational energy, particularly at ultrasonic frequencies, to overcome many of the limitations of currently known solutions for selected nerve stimulation, by achieving a nerve stimulation capability without the use of leads connected to a stimulation controller/pulse generator. It is not the intent to limit the scope of this invention to the nerves and nerve bundles in the description but rather to provide a broad solution for stimulation of any selected nerve in the body without the use of leads.
The following patents, all of which are incorporated in this disclosure in their entirety, describe various aspects of using electrical stimulation for achieving various beneficial effects by selected nerve stimulation. U.S. Pat. No. 3,835,833 titled “Method for Obtaining Neurophysiological Effects” by Limoge describes delivery and parameters for electrical stimulation in a TENS stimulation system. U.S. Pat. No. 4,690,144 titled “Wireless Transcutaneous Electrical Tissue Stimulator” by Rise et al. also describes delivery, systems, and application parameters for a TENS stimulation system. U.S. Pat. No. 6,735,475 titled “Fully implantable miniature neurostimulator for stimulation as a therapy for headache and/or facial pain” by Whitehurst et al. describes an implantable microstimulator used for treatment of pain in peripheral nerves generally in the skull or the cervical regions of the spine. U.S. Pat. No. 3,522,811 titled “Implantable Nerve Stimulator and Method of Use” by Schwartz et al. describes an implantable application for stimulation of the carotid sinus nerve as a treatment for hypertension. U.S. Pat. No. 6,615,081 titled “Apparatus and method for adjunct (add-on) treatment of diabetes by neuromodulation with an external stimulator” by Boveja describes an implantable application for stimulation of the vagus nerve as a treatment for diabetes. U.S. Pat. No. 6,684,105 titled “Treatment of disorders by unidirectional nerve stimulation” by Cohen et al. describes an application of electrical stimulation of nerves in unidirectional and bidirectional propagation of the electrical treatment along the nerve. U.S. Pat. No. 5,282,468 titled “Implantable neural electrode” by Klepinski describes an implantable neural electrode for stimulation in contact with nerve tissue. U.S. Pat. No. 5,330,515 titled “Treatment of pain by vagal afferent stimulation” by Rutecki et al. describes an implantable application for stimulation of the vagus nerve as a treatment for pain. U.S. Pat. No. 6,622,038 titled “Treatment of movement disorders by near-diaphragmatic nerve stimulation” by Barrett et al. describes an implantable application for stimulation of branches of the vagus nerve near the diaphragm as a treatment for movement disorders such as epileptic seizure, essential tremor, etc. U.S. Pat. No. 6,622,041 titled “Treatment of congestive heart failure and autonomic cardiovascular drive disorders” by Terry et al. describes an implantable application for stimulation of the cardiac branch of the vagus nerve as a treatment for congestive heart failure. U.S. Pat. No. 5,188,104 titled “Treatment of eating disorders by nerve stimulation” by Wernicke et al. describes an implantable application for stimulation of the vagus nerve as a treatment for eating disorders. U.S. Pat. No. 6,879,859 titled “External pulse generator for adjunct (add-on) treatment of obesity, eating disorders, neurological, neuropsychiatric, and urological disorders” by Boveja describes an external application for stimulation of the vagus nerve as a treatment for a variety of conditions for example, obesity, urological disorders, etc. where the application of the stimulation can be turned off and on by the patient or caregiver. U.S. Pat. No. 6,505,074 titled “Method and apparatus for electrical stimulation adjunct (add-on) treatment of urinary incontinence and urological disorders using an external stimulator” by Boveja describes an external application for stimulation of the sacral nerves and its branches as a treatment for a variety of urological conditions. U.S. Pat. No. 5,215,086 titled “Therapeutic treatment of migraine symptoms by stimulation” by Terry et al. describes an implantable application for stimulation of the vagus nerve as a treatment for migraine headache. U.S. Pat. No. 5,531,778 titled “Circumneural electrode assembly” by Maschino et al. describes an electrode design for attachment to a nerve. U.S. Pat. No. 5,251,634 titled “Helical nerve electrode” by Weinberg describes an electrode design for attachment to a nerve. U.S. Pat. No. 6,622,047 titled “Treatment of neuropsychiatric disorders by near-diaphragmatic nerve stimulation” by Barrett et al. describes an implantable application for stimulation of the vagus nerve as a treatment for neuropsychiatric disorders. U.S. Pat. No. 7,047,078 titled “Methods for stimulating components in, on, or near the pudendal nerve or its branches to achieve selective physiologic responses” by Boggs et al. describes an implantable application for stimulation of the pudenal nerve to control physiologic responses, for example for control of the urinary tract. U.S. Pat. No. 6,002,965 titled “Epidural nerve root stimulation” by Feler et al. describes treating pelvic pain by application of stimulation of nerves in the sacral and lumbar regions of the spine. U.S. Pat. No. 5,405,367 titled “Structure and Method of Manufacture of an Implantable Microstimulator” by Schulman et al. describes an implantable microstimulator used generally for stimulation of tissue. U.S. Pat. No. 6,037,704 titled “Ultrasonic Power Communication System” by Welle describes the use of ultrasound energy transfer from a transmitter to a receiver for purposes of powering a sensor or actuator without being connected by a lead/wire. U.S. Pat. No. 6,366,816 titled “Electronic Stimulation Equipment with Wireless Satellite Units” by Marchesi describes a tissue stimulation system based on a wireless radio transmission requiring the charging of a battery at the receiver and separate command signals used to control the delivery of stimulation. German patent application DE4330680A1 titled “Device for Electrical Stimulation of Cells within a Living Human or Animal” by Zwicker describes a general approach to power transfer using acoustic energy for tissue stimulation.